High speed cell sorting has been an important research technology for many years. Examples of the many applications include isolation of rare populations of immune system cells for AIDS research, isolation of genetically atypical cells for cancer research, isolation of specific chromosomes for genetic studies, and isolation of various species of microorganisms for environmental studies.
Recently, two areas of interest are moving cell sorting towards clinical, patient care applications. First, is the move away from chemical pharmaceutical development to biopharmaceuticals. The majority of new cancer therapies are developed using biotechnology. These include a class of antibody-based cancer therapeutics. Cell sorters can play a vital role in the identification, development, purification and ultimately the production of these products. Related to this is a move toward the use of cell replacement therapy for patient care. Much of the interest in stem cells revolves around a new area of medicine often referred to as regenerative therapy or regenerative medicine. These therapies may often require that large numbers of relatively rare cells be isolated from patient tissue. For example, adult stem cells may be isolated from bone marrow and ultimately used as part of a re-infusion back into the patient from whom they were removed.
High speed cell sorters have typically utilized an electrostatic droplet technology similar to that used in early ink jet printers. This method is very efficient, allowing as many as 90,000 cells to be sorted per second from a single stream. This method is not, however, particularly biosafe. Aerosols generated in the droplet formation process can carry biohazardous material. Even though “biosafe” droplet cell sorters mounted in a biosafety cabinet are commercially available, even this type of system does not lend itself to the sterility and operator protection required for routine sorting of patient samples in a clinical environment. Microfluidics technologies offer great promise for providing cell sorting capability within a closed environment. Many microfluidic systems have been demonstrated that can successfully sort cells. They have the advantage of being completely self-contained, easy to sterilize, and can be manufactured in sufficient quantities to be a disposable part. These technologies have not been widely adopted largely due to cost considerations related to the maximum throughput achievable on such a device. The fastest of these devices operate at rates of 1000-2000 cells per second, nearly ten times slower than a droplet cell sorting system. One of the speed limitations of microfluidic devices is the ability to sort desirable cells from the remaining cells quickly. All of the cells move together in a stream of fluid, and the desired cells must be routed into a collection vessel while the remaining cells are routed into a waste vessel. The present disclosure relates to a high speed means for achieving such sorting, and can be implemented in a microfluidic device incorporated into a microwell plate.